Non-reciprocating circuit device using a circulator

ABSTRACT

A wide band circulator and a non-reciprocating circuit device using such wide band circulator, in which the symmetry of the circulator characteristics is improved by dividing at least one of either the capacitive or inductive elements forming a resonating circuit resonating with a center frequency of the operational band of the circulator and inserted between an outer conductor and ground conductor of the circulator.

iliiited tates Patent [191 Konislii et a1 June 18, 1974 1 NON-RECHPRDEATENG CJRCUHT DEVICE USING A CHRCULATOR [75] Inventors: Yoshihiro Konishi, Sagamihara;

Shinsal-tu Takata, Yachiyo, both of Japan [73] Assignees: Nippon H050 Kyokai; TDK

Electronics (10., Ltd, both of Tokyo, Japan {22] Filed: May 21, 1973 [21] Appl. No.: 362,208

[30] Foreign Application Priority Data May 24, 1972 Japan 47-51524 [52] US. Cl. 333/1.1, 333/242 [51] Int. Cl. 1101p 1/32 [58] Field of Search 333/111 [56] References Cited UNITED STATES PATENTS 3,551,853 12/1970 Konishi 333/l.l 3,614,675 10/1971 Konishi 333/l.1

Primary ExaminerPaul L. Gensler Attorney, Agent, or FirmStevens, Davis, Miller & Mosher A wide band circulator and a non-reciprocating circuit device using such wide band circulator, in which the symmetry of the circulator characteristics is improved by dividing at least one of either the capacitive or inductive elements forming a res oiiatih g circuit resonating with a center frequency of the operational band of the circulator and inserted between an outer conductor and ground conductor of the circulator 5 Claims, 17 Drawing Figures Fig. l

I PRIOR ART Fig.2

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PATENTED 8W 3.818.381

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SHEET 8 OF 7 vFig.1.! 2*?! A NON-RECIPROCATING CIRCUIT DEVICE USING A CIRCULATOR BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a wide band circulator and a non-reciprocating circuit device using such a circulator or circulators. The circulator comprises a resonating system resonating with a center frequency of the operation range of the circulator. The resonating system consists of a number of reactive elements connected between the outer conductor of the circulator and the ground conductor thereof in parallel and in rotational symmetry.

2. Description of the Prior Art One of the inventors had proposed a wide frequency band circulator for increasing the operating energy for the same phase excitation in a simple construction. One example of the above circulator has been disclosed in U.S. Pat. No. 3,551,853. The inventor has also proposed a wide band isolator, for instance, In US. Pat. No. 3,614,675 using the above mentioned wide band circulator. In the above mentioned known arts, a single series resonant circuit has been used for widening the operation frequency band and which is connected between an outer conductor of a circulator and a ground conductor thereof. In such prior devices, an inductor of the resonant circuit is connected at the ground conductor side. In this practice, there is a limitation in that the space accommodating the series resonant circuit is extremely limited since for effectively increasing the same phase excitation energy the series resonant circuit should be connected between a location of center axis of the outer conductor of the circulator and ground and the inductive element of the resonant circuit should be connected to the ground also at a position of the center axis of the circulator. On the other hand, there is a requirement for a circulator in that a DC magnetic field should be effectively applied to the ferrite plates arranged at both sides of the inner conductor and in order to satisfy this requirement the space for accommodating the above mentioned resonating circuit should be made as compact as possible.

The known wide band circulators of the above type have a further disadvantage in that their characteristics vary greatly depending upon the location where such series resonant circuit is connected. The symmetry of the characteristics may greatly be deteriorated depending upon the location of the series resonant circuit. In order to obtain a wide band circulator having excellent characteristics, the location of-such a resonating system should carefully be selected to satisfy the poisitional symmetry with respect to all of the exciting input ports. However, in such known art using a single resonating system, the symmetrical position relationship for each of the input excitation positions is very difficult to realize and in a view of the requirement for the miniaturization of the device it has been impractical to realize a suitable construction for satisfying the above requirements.

SUMMARY OF THE INVENTION The present invention has for an object to mitigate or minimize the above mentioned disadvantages of circu lators of the known type and to realize a circulator having an excellent symmetry of the characteristics with respect to all of the terminals as well as an invention which is suitable for miniaturization and manufacturing in mass-productive manner. The present invention further relates to a non-reciprocating circuit device having a wide operation band using such a wide band circulator of excellent symmetry.

A further object of the present invention is to realize a circulator particularly suitable for use in a certain object of the overall device. The circulator is realized by providing a plurality of resonating circuits or a plurality of resonating elements forming a resonating circuit for realizing a wide band circulator and inserted in the circulator between its outer conductor and the ground conductor. The invention also relates to a nonreciprocating circuit device utilizing such circulators.

A still further object of the present invention is to realize a miniaturized non-reciprocating circuit device suitable for mass-production and including the above mentioned wide band circulator particularly designed for a special task of the circuit.

In one aspect of the present invention, a wide frequency band circulator is provided with a resonating system for resonating a center frequency of the operation range of the circulator which system is connected between the outer conductor and the ground conductor of the circulator and of which the resonating system is formed by a plurality of resonating circuits connected in parallel or a plurality of circuit elements forming a part of such parallel circuits.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an equivalent diagram of a wide frequency band circulator of the known type;

FIG. 2 is a schematic view for explaining the construction of the Wide frequency band circulator of the known type shown in FIG. 1;

FIGS. 3, 5 and 7 are the equivalent diagrams showing possible embodiments of wide frequency band circulators according to the present invention;

FIGS. 4, 6 and 8 are schematic views for explaining the construction of the wide band circulators according to the present invention of which equivalent circuit diagrams are shown in FIGS. 4, 6 and 8;

FIG. 9 is a graph illustrating the characteristics of a circulator of the known type;

FIG. 10 is a graph showing the characteristics of a wide frequency band circulator according to the present invention;

FIG. 11 is a simplified diagram for explaining a nonreciprocating circuit device using the wide band circulator according to the present invention;

FIG. 12 is a characteristic diagram of the circuit shown in FIG. 11;

FIG. 13 illustrates a diagram of a particular application of the non-reciprocating circuit device according to the present invention;

FIG. 14 is a diagram for illustrating a further embodiment of the application of the non-reciprocating circuit device according to the present invention;

FIG. 15 is a simplified cross sectional view for illustrating the principal construction of the nonreciprocating circuit device using a circulator according to the present invention;

FIG. 16 is an equivalent diagram of a resonating circuit to be used in the device of the present invention; and

FIG. 17 shows a practical embodiment of one example of construction of the resonating system used in the circulator of the present invention, in which a right side view and plan view of the resonating system are shown.

DESCRIPTION OF THE PREFERRED EMBODIMENT In order to provide a better understanding of the present invention, at first, a wide frequency band Y- circulator of a known type, such as disclosed in the aforementioned patents or patent application, will be explained briefly.

FIG. 1 is an equivalent diagram and FIG. 2 is a schematic view for showing a typical construction of such a Y-circulator. The circulator has three coaxial feeding terminals 1, 2 and 3 arranged in rotational symmetry. In FIG. 2, only two terminais I and 2 are shown by reason of simplifying the drawing. At the central portion of the FIG. 2, LE generally shows a lumped element type circulator. The lumped element type circulator LE has an inner conductor 4. The inner conductor 4 consists of meshed conductors formed by three groups of conductors, each of which group consists of at least two parallel conductors extending from each one of said three coaxial feeding terminals 1, 2 and 3 and terminating at the opposite wall of an outer conductor 6 of the lumped element Y-circulator. Said group of conductors intersect with conductors of the other group at an angle of 120 in case of a three terminal Y-circulator. Crossing points thereof are so arranged as to evenly distribute with respect to surfaces of a pair of ferrite plates 5. The crossing points are insulated to avoid short-circuit of the intersecting conductors. Each of the feeding terminals l, 2 and 3 is connected with an end of a capacitor C of which the other end is connected to the outer conductor 6. The capacitors C are provided to vary the permeability of the ferrite plate 5 substantially uniformly. The outer conductor 6 of the lumped element Y-circulator LE is insulated from a ground conductor 7 which forms a casing or a support for the circulator. Between the outer conductor 6 and the ground conductor 7, there is connected a series resonant circuit L C consisting of a series connection of a capacitor C and an inductor L The series resonant circuit L C is chosen to substantially resonate with a center frequency of an operating frequency band of the circulator for widening the frequency band. A pair of permanent magnets 8 are provided in order to apply a dc magnetic field to the ferrite plates 5.

Referring to the equivalent diagram shown in FIG. 1, capacitance C and inductance L connected to each of the coaxial feeding terminals 1, 2 and 3 represent capacitive and inductive elements of the above mentioned lumped element Y-circulator LE. L and C represent the series resonant circuit for resonating substantially the center frequency of the operating frequency of the circulator.

Such a known wide band circulator, which had been used in a conventional non-reciprocating device, has a drawback in that the resonating circuit L C used for the purpose of widening the frequency band is connected between one point of the outer conductor 6 and one point of the ground conductor 7. According to such single connection of the resonating circuit L C the circulator characteristics will vary greatly depending upon the position of said connection.

FIG. 9 illustrates a characteristics diagram showing the relation between forward loss and backward loss vs frequency and a relation between voltage stationary wave ratio (VSWR) vs frequency of a circulator of a known type as referred to in the above. As can be seen from FIG. 9, owing to the reason that the resonating circuit is connected between one point of the outer conductor of the circulator and one point of the ground conductor the characteristics will vary greatly depending upon the location of the excitation. In other words, symmetric characteristics with respect to the feeding terminals are greatly distorted. In FIG. 9, a curve A corresponds to the characteristics between the coaxial feeding terminals 1 and 2, a curve B corresponds to those between the terminals 2 and 3, and a curve C corresponds to those between the terminals 3 and 1.

According to the present invention, in order to improve the symmetric characteristics of a circulator, at least one of the circuit elements of L and C in the series resonant circuit for resonating at a frequency substantially at the center of an operational range of the circulator is divided into a plurality of circuit elements, and each of the thus divided plurality of circuit elements is connected between the outer conductor and the ground conductor of the circulator in a manner in which they are arranged in rotational symmetry.

The principle of the present invention will be explained by referring to FIGS. 3 to 8.

FIG. 3 shows an equivalent diagram of one embodiment of the present invention in which the capacitive element C is provided in common and the inductive element is divided into three elements of L's, Ls and L"s. FIG. 4 shows a greatly simplified schematic view of the circulator shown in FIG. 3.

FIG. 5 shows an equivalent diagram of another embodiment, in which the inductive element L of the series resonant circuit is provided in common and the capacitive element is divided into three portions C's, Cs and C's. FIG. 6 shows a corresponding schematic view of the wide band circulator of which an equivalent diagram is shown in FIG. 5.

FIG. 7 shows a still further embodiment of the present invention in which both of the inductive elements and capacitive elements of the resonating system are divided into three portions L's, C's; L"s, C"s; L's, C"s; and FIG. 8 shows schematic view thereof.

In the embodiments shown in FIGS. 7 and 8, it is apparent that the capacitive element C's, C"s and C"'s may be connected in the ground side in the respective series resonant circuits.

In the above mentioned embodiments the overall resonant frequency of the resonating system formed by three divided circuit elements should be so selected as to satisfy the resonant frequency requirement as required for the wide band purpose. The value of each inductive element and that of each capacitive element should be selected to satisfy this requirement at the overall impedance value.

One practical embodiment showing an actual construction of the wide band circulator according to the present invention of which the equivalent circuit corresponds to FIG. 4 is shown schematically in FIG. 15.

FIG. 10 shows frequency characteristic curves of transmission loss and VSWR of a non-reciprocal device using a wide band circulator having three terminals made in accordance with the present invention. In the figure, curves A, B and C represent characteristic curves between respective terminals 12, 2-3, and 3-1, respectively as has been explained with reference to FIG. 9. By comparing FIG. with FIG. 9 it will be apparent that symmetry of the circulator characteristics according to the present invention is much improved over the prior art in both the frequency characteristics of the loss and VSWR.

In the foregoing, the present invention has been explained with respect to a Y-circulator having three terminals. However, the same principle of the present invention can be applied to a case in which a different number of terminals are provided so as to obtain symmetrical characteristics of the circulator.

As a practical application of the wide frequency band circulator of the present invention, an embodiment of non-reciprocating circuit device will be explained hereinafter.

FIG. 11 showsa principle of an application of a wide band circulator of the present invention into a nonreciprocating circuit device. In FIG. 11, CY generally shows a circulator having terminals land 2 forming input and output terminals. Third terminal 3 is connected to the outer conductor through an absorbing resistor R. The outer conductor of the circulator CY is connected to ground through a series resonant circuit L,C, having a resonating frequency f, in the operational frequency range of the circulator CY. In order to simplify the drawing and explanation, the series resonant circuit L,C, is shown as a single element, however, it should be understood that the series resonant circuit L,C, is so formed as to satisfy the above principle of the present invention explained with reference to FIGS. 3 to 8. The outer conductor is further connected to ground through a further series resonant circuit L',C, having a resonating frequency f which is outside the operational frequency range of the circulator. This circuit device has the same function as an isolator at the frequency f, as has been explained in the aforementioned US. Pat. No. 3,614,675. This means that energy having frequency f, supplied to terminal 1 passes the circulator CY without substantial loss to terminal 2 and contrary thereto energy having frequency f, supplied to terminal 2 is nearly completely damped and absorbed by the absorping resistor R and does not appear at terminal 1. At the frequency f, the circuit is assumed to have a band-eliminating filter formed by the series resonant circuit L',C', having resonating frequency f, connected in parallel with the transmission path between the terminals 1 and 2. At this frequency f, the circuit operates reciprocally, while at the frequency f, the circuit operates non-reciprocally.

FIG. 12 shows the frequency characteristics of transmission loss of the circuit device shown in FIG. 11. On the left half of FIG. 12, a broken line shows backward loss or loss in a direction from terminal 2 to terminal 1. On the right half of FIG. 12, a full line shows forward loss or loss in a direction from terminal 1 to terminal 2. These characteristic curves illustrate a fact that the circuit operates non-reciprocally at the frequency f,, and reciprocally at the frequency f,. Forward loss at frequency f, has not been shown for purposes of simplifying the drawing but it should be noted that the forward loss at the frequency f, is very small and in an order as shown in FIG. 10.

The above circuit shown in FIG. 11 may conveniently be used in a circuit, for example, in a common trans- 6 mitting'and receiving circuit, output mixing circuit of a transmitter, etc.

FIG. 13 shows one practical application of such a non-reciprocating circuit device shown in FIG. 11 to a common transmitting and receiving circuit. In FIG. 13, CY, is a wide band circulator and CY is a nonreciprocating circuit device such as shown in FIG. 11. An output terminal of a transmitter TX, is connected to one terminal of the wide band circulator CY,. A receiver for receiving a frequency f, is connected to the other terminal of the circulator CY, through a frequency band selector B, for passing frequency f, to the receiver REC and passing frequency f to an absorbing resistor R,. A further terminal of the circulator CY, is connected to a terminal of the non-reciprocating circuit device CY of which one terminal is connected to an antenna A and the other terminal is connected to the outer conductor through a band-eliminating filter B having an eliminating band at a frequency f,. The non-reciprocating circuit device is further connected to ground through two resonating circuits for resonating frequencies f, and f,, respectively. It is assumed that the transmitter TX, transmits an output having frequency f, and also a spurious component having frequency f,. The spurious component 1", is reflected by a series resonant circuit L,C', having resonating frequencyf', and connected to the non-reciprocating circuit device CY and returned toward the circulator CY, andis supplied to the frequency band selector B, and absorbed by an absorbing resistor R, connected thereto. Accordingly a spurious electro-magnetic wave f, emanating from the transmitter TX, is not transmitted from the antenna A.

On the other hand, an incoming wave to be received by the receiver REC from the antenna A having frequency substantially at the frequency f, is reflected by the band-eliminating filter B connected to the circuit CY and passed to the circulator CY, and received by the receiver REC through the frequency band selector 8,.

By the abovementioned principle, the circuit as shown in FIG. 13 can prevent emanation of spurious irradiation'from the transmitting antenna and at the same time the same antenna is used for the reception of a receiving wave.

FIG. 14 shows another embodiment of an application of the non-reciprocating circuit device of the present invention. The embodiment shown in FIG. 14 is a transmitting circuit for two transmitters TX, and TX A transmitter TX, is coupled to an antenna A via a circulator CYl and a nonreciprocating circuit device CYl and through a coupling network N. Another transmitter TX is coupled to the same antenna A via another circulator CY2 and non-reciprocating circuit device CY2 and through the coupling network N. Both groups of devices CYl, CYl and CYZ, CY2 correspond to the aforementioned construction of the circuit shown in FIG. 13 so that a detailed explanation is omitted. The transmitter TX, transmits electromagnetic waves of frequency component f, and a spurious components f The transmitter TX transmits frequency component f and spurious component 1%. In the same manner as has been explained with reference to FIG. 13, the necessary frequency components f, and f are transmitted from the antenna A. However, the spurious components 1", and f are absorbed by absorbing resistors R, and R; connected to the circulators CYl and CYZ. Accordingly, such spurious mode output electro-magnetic waves are not irradiated from the antenna A so that a very high quality transmission coupling circuit can be realized.

FIG. 15 illustrates one actual construction of a nonreciprocating circuit device using a circulator of which an equivalent circuit diagram is shown in FIG. 3.

The non-reciprocating circuit device according to the present invention and particularly the resonating circuit portion may conveniently be formed by a print ing circuit technique and other practice suitable for mass-production. The non-reciprocating circuit device can be miniaturized by introducing such printing circuit technique, etc. and is used very conveniently in various applications.

In FIG. 15, 10 generally indicates a nonreciprocating element portion formed by magnetic ma terials such as ferrite plates and the inner conductor. The non-reciprocating element 10 is housed inside of an outer conductor 11. 12 shows the yoke portion of a pair of permanent magnets 13. 14 is a substrate or base plate for providing a connection of the inner conductor and 15 is a resonating system, of which an equivalent curcuit diagram is shown in FIG. 16 and one example of a structural view is shown in FIG. 17.

It is preferred to manufacture the resonating system for rotational symmetry with respect to center axis of the circulator in order to obtain symmetry of the circulator characteristics and also in view of convenience for production. Accordingly, various circuit elements are arranged in the rotational symmetries manner with respect to the axis of the circulator and the connections are also made at points arranged in rotational symmetry. By a same reason, the outer conductor 1] may preferably be arranged in rotational symmetry.

FIG. 17 shows one example of the resonating system to be used in the improved wide frequency band Y- circulator of the present invention. The resonating system is provided on a insulating substrate 14 having a very small dielectric loss. An oppositely arranged electrode 16 provided on the insulating substrate 14 with respect to a ground conductor provided on the other side forms a capacitance portion C Three strip line portions 17 extending radially in three directions from the electrode 16 and bent along the circumference form the inductance portion Ls (L's, L"s, L's). These resonating systems may be provided by vaporization in a very simple manner. According to this practice a miniaturized wide frequency band circulator suitably manufactured by mass-production can be realized.

In FIG. l7, 18 illustrates connecting portions to the ground conductor applied at the other side of the insulating substrate 14. In the right side view, the strip line portion 17 and the connecting portion 18 are not shown in order to show the portion of the electrode 16. By providing through holes in the substrate 14 and by providing said electrode or strip conductors on the both sides of the base plate and by using a number of such substrates, the capacitance and inductance of the resonating system can be increased according to the need.

According to the present invention, a nonreciprocating circuit device having a desired characteristic in the pass-band of the circulator can be obtained by providing the resonating system divided into a plurality of portions or elements which are connected between the outer conductor and the ground conductor. Further advantage can be expected in that one end of the resonating system can be arranged at a very closed location of each of the terminals of the circulator. According to this second merit of the construction the adjustment of the connecting point becomes very easy which in turn facilitates easy adjustment of the characteristics during manufacture of the device thereby facilitating the manufacturing process.

The overall device can be made very flat shaped. As mentioned above, by providing the resonating system and its capacitance and inductance portions by the printing technique or by vaporization a very miniaturized wide frequency band circulator suited for easy mass-production can be realized.

What is claimed is:

I. A non-reciprocating circuit device including a circulator which has an inner and outer conductor and is mounted on a ground conductor, the outer conductor of the circulator being insulated from the ground conductor with respect to high frequency energy, and circuit means including a resonating system for resonating at a center frequency of the operational frequency range of the circulator and connected between the outer conductor and the ground conductor, wherein said resonating means comprises a plurality of circuit elements being arranged in parallel between the outer conductor and the ground conductor.

2. A non-reciprocating circuit device as claimed in claim 1, wherein said resonating system includes a number of parallel connected identical circuit elements.

3. A non-reciprocating circuit device as claimed in claim 1, wherein the plurality of circuit elements are arranged in substantially rotational symmetry with respect to a center axis of the circulator.

4. A non-reciprocating circuit device as claimed in claim I, wherein the plurality of circuit elements are arranged on at least one surface of an insulating plate.

outside the operational frequency range.

a: a =i 

1. A non-reciprocating circuit device including a circulator which has an inner and outer conductor and is mounted on a ground conductor, the outer conductor of the circulator being insulated from the ground conductor with respect to high frequency energy, and circuit means including a resonating system for resonating at a center frequency of the operational frequency range of the circulator and connected between the outer conductor and the ground conductor, wherein said resonating means comprises a plurality of circuit elements being arranged in parallel between the outer conductor and the ground conductor.
 2. A non-reciprocating circuit device as claimed in claim 1, wherein said resonating system includes a number of parallel connected identical circuit elements.
 3. A non-reciprocating circuit device as claimed in claim 1, wherein the plurality of circuit elements are arranged in substantially rotational symmetry with respect to a center axis of the circulator.
 4. A non-reciprocating circuit device as claimed in claim 1, wherein the plurality of circuit elements are arranged on at least one surface of an insulating plate.
 5. A non-reciprocating circuit device as claimed in claim 1, wherein said circuit means comprises a plurality of series resonant circuits in which one series resonant circuit resonates with a frequency in the operational frequency range of the circulator and another of the series resonant circuits resonates with a frequency outside the operationAl frequency range. 